We were at BWV December 28th through January 2nd this year. The crowds on New Year's Eve were incredible! We got Fast Passes for what we could, and forgot about the rest for that day. The Magic Kingdom closed to non-resort guests at 10:0am, as did Animal Kingdom. We were lucky to be staying in the Boardwalk-side Grand Villa, one level up from the stores. We had 6 adjoining balconies, so plenty of room for all of our guests and family. My husband tried to take our 11 yr old, and his best friend to Epcot to use the Fast Track FP on New Year's Eve, and promptly lost the boys in the swelling (and rowdy) crowd. Lucky for us, the WDW Security Dept., is unparalleled!
We gave up, and watched the festivities from the Villa. What a view! We could see the Epcot fireworks, the MGM fireworks, and I think the Animal Kingdom ones, all at once! What a sight!
I think you definitely need to prepare for a crowd, don't expect to do everything, and go with the flow. That being said, I'd do it again in a heartbeat!